1. Field of the Invention
The invention relates to a power supply system and, more particularly, to a power supply circuit between an electronic device and an extension dock.
2. Description of the Related Art
Since the demand of the mobile products on extension devices including a battery module increases, such as an external keyboard, an external hard disk, an external CD-ROM driver, and an external card reader and other external dockings, the design on the power of the external docking becomes more important. However, if the circuit and the control logic in the extension dock can be decreased, the cost and the volume for the product are reduced.
Generally, when an electronic device is connected with an extension dock, a power path is formed between the electronic device and the extension dock. The power path is used to transmit the power signal between the electronic device and the extension dock. Generally, while converting the power direction, the current direction in the power path should be controlled after both the state of the electronic device and the extension dock are determined. It can avoid that electric signals with different specifications of the extension dock are directly transmitted to a battery of the electronic device without adjustment, which may damage the battery.